Dry kiln



Sept. 30, 1930 F. M. CREIGHTON DRY KILN 5 Sheets-Sheet l Filed Sept. 16, '1925 Sept. 30, 1930. cRElGHTON 1,777,255

DRY KILN Filed Sept. 16. 1925 3 Sheets-Sheet 3 V V V fl 17 J7 7 I n'uvnto'a W 2 I w Patented Sept. 30, 193

FRANK M. CREIGHTON, OI AMERICUS, GEORGIA, ASSIGNOR 'I'O MOORE DRY KILN COM- PANY, F JACKSONVILLE, FLORIDA, A CORPORATION OF FLORIDA DRY KILN' Application filed. September 16, 1925. Serial No. 56,770.

My invention relates to an improvement in 7 dry kilns.

An object of the invention'is to increase and control the circulation in progressive kilns, especially long progressive kilns, by an outside fan, or any other circulating means, located outsidethe kiln, and connected with ducts communicating with the interior of the kiln. This improvement is of especial advantage in long progressive kilns in which it is desirable to speed up the circulation, especially longitudinal circulation to .produce more rapid and uniform drying of the stock and to prevent a great differential in the condition of heat and humidity at the two ends of the kiln. It is also of especial advantage in drying refractory lumber which requires definite conditions of heat and humidity at the green end, center, and dry end of the kiln. It also causes rapid uniform drying when a low temperature and relatively high humidity are carried in the kiln, or when special conditions of heat and humidity are desired at certain points in the kiln, for instance at the green end, center, or dry end. This present invention therefore includes a kiln in Which the drying conditions at the various positions or stages can be properly regulated.

Another object of the invention is to provide a kiln in which the drying operation will be more rapid than in natural draft kilns, and at the same time enable the operator to dry a much better grade of stock.

For this purpose, the invention includes a graduated heating system, with steam sprays, an outside fan or circulator for aiding the air circulation, and ducts for letting air into the kiln at predetermined points, whereby the heat and humidity of the ends and center sections of the kiln are under control and are rendered more uniform by maintaining a positive circulation through the loads oflumber,,all of which is accomplished by the use of the graduated heating system combined with the outside fan, distribution and collecting ducts, fresh air ducts, ventilators and sprays. All these factors are combined and made to work together to producethe correct distribution of heat, humidity and circulation throughout the kiln. v Progressive kilns, especially long progressive kilns, in the past have maintained too slow a longitudinal-turnover of air to maintain a correct distribution of heat and humidity at all parts of the kiln. At the green end the heat is often too low, and the humidity too high, whereas, at the dry end the heat is often too high and the humidity too low. These conditions are remedied by creating a controlled longitudinal circulation, which can be regulated to obtain the desired heat and humidity distribution throughout the'kiln, which circulation is produced through the loads of lumber instead of around them, as has been the tendencyheretofore.

This invention also includes means for producing a reversal of circulation at the ends of the kiln. The circulation is down through the lumber at the green end and up through the lumber at the dry end, which gives a uniform drying of the lumber. The tendency of the tops of the loads of lumber to dry faster at the green end is compensated for by the tendency of the bottoms of the loads to dry faster at the dry end, and the result is uniformly dried loads of lumber.

Another object of this invention is to make a more eflicient use of the graduated heating system. The graduated heating system is one of the most important elements of a properly designed progressive kiln. The minimum heat at the green end and the maximum heat at the dry, end are requirements which in themselves are indispensable, but this auxiliary means emphasizes the value of the distribution by sucking the moist spent air, which has passed through the lumber into the ducts below the tracks at the green end, giving it motion by means of fans and re-delivering it to the dry end through the coils and sprays which properly heat and humidifyit before it is forced through the lumber at the dry end. In doing this, circulation is produced through the loads of the lumber at the dry end instead of around them.

Still another and a very important object of this invention is to produce circulation in the kiln, not around, but through the lumber. Circulation takes. place in loads of lumber by natural means. A down circulation through the load is had at the green-end of the kiln where the lumber is of relatively higher moisture content, due to the cooling effect of evaporation. This invention covers combining all factors such as sprays, coils and ducts to work with this natural circulation to produce downward circulation through the load at the green end of the kiln. At all other points except at the green end, there is a tendency for the circulation of air to pass around the loads, as this is the course of least resistance; but this invention provides a rapid circulation in the kiln through the lumber at these points in addition to working with a natural longitudinal re-circulation, which is ordinarily maintained in a progressive kiln. This invention produces a more positive recirculation than has been heretofore obtained because a greater control is had over the air in the kiln. Thisis obtained by reason of the fact that an outside fan is used, and the speed ofthe fan may be regulated to deliver just as much air to the dry end of the kiln, and to withdraw just as much air from the green end of the kiln, as maybe desired for any particular kind of lumber. The size of inlet ducts and openings inside the kiln at green end, also the outlet of delivery ducts, inside the kiln at dry end, may be varied as desired, to give 'the desired circulation and distribution to suit any particular stock for which the kiln is built.

In the accompanying drawings:

Fig. 1 is a longitudinal vertical section through a kiln constructedin accordance with my invention;

. F g. 2 is a horizontal sectional view through the same; A

Fig. 3 is a transverse sectional view on the line 3-3 of Fig. 1 B Fig. 4 is a similar view on the line 4.-4 of Fig. 5 is a longitudinal vertical sectional view through a kiln showing a modified form of circulating systemas used for cross-piling;

Fig. 6 is a horizontal sectional view through the same; i

Fig. 7 is a transverse sectional view on the line 77 of Fig. 5;

Fig. 8 is a diagrammatic sectional view showing my invention as applied. to a battery of kilns; and

Fig. 9 is a detail sectional view of one of the air outlets in the ducts.

A, represents a kiln of the progressive type with the green end shown at the left, and the dry end at the right, with the usual rails l on which the trucks travel through the kiln in %he direction of the arrow at the left-hand enc.

IVhile various types of heating system might be employed, the one shown is a graduated heating system 2, which preferably starts some distance in from the green end and extends approximately to the dry end, the bottom header 3 being located part way in from the starting point of the heating system, and the top header 4 part way between the bottom header 3 and the dry end, thus giving two leads of pipe toward the green end, three midway, and four at the right hand or dry end, so that the kiln might be said to be divided into four sections or zones, the first at the green end where there is less heat in this particular kiln, the second and third increasing, and the fourth where it reaches the highest point toward the dry end.

Air may be supplied through the cold air openings 6, as desired, at the dry end of the kiln. In Figs. 1 to 4, inclusive, the kiln is shown as having the ducts 8 at the green end thereof, which are provided with a plurality of openings 9 which are plain sl'ots or crack openings for collecting air from this green end of the kiln where it is sucked by means of the fan 10 into the delivery duct 11 after having been mixed with fresh air from the openings 12. The delivery duct 11 terminates in the ducts 1313 at the dry end of the kiln, which have the openings 14 therein similar to the openings 12 except they have scoops 15 for directing the air upwardly into the kiln, and also side plateslo for inducing greater circulation by means of the injector principle. From these openings 14 the air is forced up through the heating system into the kiln.

An independent cold air duct 28 may be located at the dry end of the kiln to be used in the event that the auxiliary recirculating means is not used. In other words, if the kiln were to be used as a straight natural draft kiln without auxiliary means of producing circulation, it may require a fresh air duct at the dry end thereof. The duct 28 is shown as having slitted apertures in the top thereof for admitting air into the kiln.

The humidity of the air is provided for by sprays located at different points. The sprays 17 are located toward the top of the green end, and the sprays 18 at or near the bottom near the dry end, andpreferably a little above and in close proximity to the vfloor ducts 13, through which air is forced from the bottom of the kiln in an upward direction through the heating-coils, whence it is circulated in a direction as indicated by the arrows toward the green end.

The sprays and their duct location may vary, but they are placed always in such a position to humidify the air before it enters the lumber pile and also so that the force of the sprays is used to help produce a circulation through the lumber instead of around it. This arrangement is indicated in the drawings where both cross and endwise piling is dinal circulation, as indicated by arrows in Fig. 1, tends to evade the loads in most cases. The sprays are thus placed to help guide this circulation through the lumber instead of aroundit.

In drying slow drying hardwoods where it is desirable to maintain moisture in the "kiln and also to conserve heat, by reducing ventilation, the ventilators V draw air from just above the floor line of the kiln, or from the region of lowest air temperature and greatest air density, as shown in Fig. 1. In drying other quick drying woods, containing high percentage of moisture content, ventilators are in roof.

The type of kiln shown in Fig. 5 is intended for cross-piling of the lumber and for this purpose it has the top and bottom spray pipes 19 and 20 respectively arranged transversely of the kiln, so as to spray downwardly and upwardly respectively through the lumber. This kiln further difiers from that shown in Figs. 1 to 4, in that the delivery duct 11 is drawn by means of a fan 23 on the outside of the kiln, the fan forcing the air through the delivery duct 24 into the several kilns.

The delivery duct openings are arranged below the piles of lumber so that the auxiliary circulation of the ducts will be forced through the loads instead of allowing the circulation to spread around the same as is the natural tendency at thedry end. Furthermore, these delivery openings are shown in proximity to the maximum amount of pipe in the heatlng system and as delivering the air through this maximum amount of heating pipe. In other words, there is a direct relation between the deliverin duct system at the dry end and the maximum amount of heating pipe through the kiln. 'I hese ducts are made as large as possible inorder to reduce friction, resistance, and static pressure. When steam sprays are used in the kilns, they must be so located as to help the auxiliary air from the duct system to produce a circulation through the loads instead of around the same. This is done by locating the sprays directly above the outlets from the ducts of the dry end so that they will blow into the loads. The spray is thus a lead to aid the movement of the air from the delivery duct into the loads.

Variations in the operating system may be necessary at times to give the necessary distribution of heat and humidity at various sections or stages in-the kiln.

I claim:

1. A progressive kiln having green and dry ends, a graduated heating system therein of progressively increasing intensity toward the dry end, a fan located exteriorly of the kiln communicating with the green end thereof, suction ducts communicating with the fan for withdrawing air from the green end of the kiln, means for supplying fresh air to said fan, delivery ducts communicating with the fan for delivering the fresh air and withdrawn air from the fan to the dry end of the kiln, overhead spray pipes located at the green end of the kiln and underneath spray pipes located at the dry end of the ldln and immediately above the delivery ducts, for increasing the circulation through the material being treated, and an auxiliary fresh air duct extending inwardly at the dry end of the kiln.

2. In a drying apparatus of the progressive type, a heating system includin a relatively short pass at the dry end for t e initial introduction of heating media and connected with and discharging into relatively long passes extending toward the fgreen end.

3. In a drying apparatus 0 the progressive type having green and dry ends, a heating system including relatively short steam-pipes approximately at the dry end for the initial introduction of steam, and connected with and discharging into steam. pipes leading toward the green end.

4. In a drying apparatus of the progressive type having green and d ends, means for introducing a heating me ia at a point between the center and dry end of the apparatus, and means for directing said heatmg media toward the dry end after introduction thereof, thence back toward the green end.

In testimon whereof I afiix mysignature.

RANK M. CREIGHTON. 

